ABS through aggressive stitching

ABSTRACT

Aggressive (i.e. tight tolerance) stitching offers several advantages for magnetic write heads but at the cost of some losses during pole trimming. This problem has been overcome by replacing the alumina filler layer, that is used to protect the stitched pole during trimming, with a layer of electro-plated material. Because of the superior step coverage associated with the plating method of deposition, pole trimming can then proceed without the introduction of stresses to the stitched pole while it is being trimmed.

FIELD OF THE INVENTION

The invention relates to the general field of magnetic write heads withparticular reference to pole trimming.

BACKGROUND OF THE INVENTION

The stitched writer has been the major workhorse of the data recordingindustry for the past several years due to its capability to providenarrow track width as well as for its tolerance control. On the otherhand, the planar writer has proven to have better mechanical behaviordue to its planar and non-recessed structure. Both writer designs can,however, be further improved by adopting aggressive stitching techniquesto overcome the following problems.

A. FIG. 1 illustrates a LDCR (low DC resistance) write head which is anexample of a stitched writer design. Seen there are shielding layers 11and 12 (11 being part of the reader head which is not shown), lower pole13 (P1) and stitched pole 16 (P2). Also shown are coils 14, insulation17, and upper pole 15 (P3). Not shown, but necessarily present, is awrite gap between 15 and 16. The recession of P3, 15, relative to P2,16, can impact over-writing, write saturation, and adjacent trackerasure. With smaller track width, one can further enhance the writingcapability and write saturation by reducing the recession and byensuring balanced adjacent track erasure. However, the integrity of thealumina that is used to fill in the P3 recession area (element 18) turnsout to be a problem due to poor step coverage by the alumina.

B. FIG. 2 illustrates an example of a planar writer. Seen there areshielding layers 11, 12, and 13 (11 being part of the reader head whichis not shown). Lower pole P1 is made up of three parts, 24, 25, and 26while P2 is upper pole 15. Also shown are coils 14 and insulation 17. Asnoted above, not shown, but necessarily present, is a write gap between15 and 26. For this type of design, ATE (adjacent track erasure) is aserious problem. Either the P2 flank field or the P1 field induces theATE problem. A reduction of the P2 flank field can be achieved by usinga P2 step design, as show, but to further reduce the P1 field induced bythe PPT (perpendicular pole trim) process, one needs to either recess aportion of P1 or further extend P1 to enhance the P1/P2 coupling.However, having a recessed P1 portion gives rise to the same aluminaintegrity problem discussed above, i.e. the poor alumina step coverageassociated with element 28.

The present invention discloses how to overcome the alumina integrityproblem at the ABS (air bearing surface). The invention makes possibleboth aggressive P3 stitching as well as aggressive P1 recession withoutany of the problems associated with the alumina integrity.

A routine search of the prior art was performed with the followingreferences of interest being found:

In U.S. Pat. No. 6,608,737, a Headway patent, Han et al. show a platedP2 where Ps is stitched to P2. In U.S. Pat. No. 6,591,480, Chen et al.disclose forming both poles by plating where an upper pole yoke isplated over the upper pole piece.

SUMMARY OF THE INVENTION

It has been an object of at least one embodiment of the presentinvention to provide a process for pole trimming a stitched writerwithout causing any accessory damage thereto.

Another object of at least one embodiment of the present invention hasbeen that said writer be a LDCR write head.

Still another object of at least one embodiment of the present inventionhas been that said writer be a planar writer.

A further object of at least one embodiment of the present invention hasbeen to provide the structures that derive from said trimming processes.

These objects have been achieved by replacing the alumina filler layer,that is used to protect the stitched pole during trimming, with a layerof electro-plated material. Because of the superior edge coverageassociated with the plating method of deposition, pole trimming can thenproceed without the introduction of stresses to the stitched pole whileit is being trimmed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a LDCR write head of the prior art.

FIG. 2 shows a planar write head of the prior art.

FIG. 3 illustrates the formation of the first of two photoresist moldsfor use in depositing the upper magnetic pole of a LDCR writer.

FIG. 4 shows the upper pole in place.

FIG. 5 shows how the mold shown in FIG. 3 may be enlarged through asecond exposure through a new mask.

FIG. 6 shows how a layer of non-magnetic material is electro-depositedwithin the mold of FIG. 5.

FIG. 7 shows the lower pole and coil well of a planar writer.

FIG. 8 shows how a layer of non-magnetic material is electro-depositedover the step that is part of the lower pole's upper surface.

FIG. 9 shows the structure of FIG. 8 after planarization and formationof the upper pole.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

We will disclose the present invention through a description of improvedprocesses for the manufacture of both LDCR and planar writers. Thesedescriptions will also make clear the structures that are claimed.

1^(st) Embodiment (LDCR Writer)

Referring now to FIG. 3, the process begins with the provision of lowermagnetic pole 31 (for purposes of simplification, elements 12, 13 and 16are shown as single element 31) in which we form a cavity which containswrite coils 14. The latter are coated with layer of insulation 17 a andextend above the cavity by between about 3 and 5 microns. A seed layer(not shown but needed to initiate the plating) coats 17 a. As seen, thecavity that contains the coils is fully filled.

The structure is then coated with a layer of a positive photoresistwhich, by exposing through a first mask and then performing a firstdevelopment, gets patterned into mold 32 which surrounds coils 14 butleaves areas 33 at the top surface of lower pole 31 exposed. These areaare typically between about 2 and 4 microns wide.

In the next step, illustrated in FIG. 4, upper magnetic pole 41 is laiddown inside mold 32 by means of electroplating. Then, in a key stepillustrated in FIG. 5, mask 32 is exposed through a second mask and asecond development is performed. The result is the transformation ofmold 32 into mold 52. The latter has a larger internal width than mold32 so additional amount 53 of the top surface of 31 gets uncovered,typically by between about 1 and 2 microns.

As a key feature of the invention, this is followed by the deposition,through electroplating, of layer of non-magnetic material 61 on uppermagnetic pole 41 as well as the exposed areas 53. Our preferredmaterials for electroplated layer 61 have been any of NiPd, NiP, orNiCu, but any non-magnetic electro-platable material could have beenused.

The process concludes with the removal of mold 52 followed bysimultaneously polishing both magnetic poles until the ABS level isreached, making sure that some thickness of non-magnetic material 61remains. Except for the presence of layer 61, The final structure is asseen in FIG. 1 except that element 18 is now (non-magnetic) metal ratherthan alumina. Because it was deposited through electroplating, thereplacement for element 18 has good step coverage and polishing may beterminated arbitrarily close to upper pole 15 without stressing it.Typically the thickness (in a direction normal to the ABS) of thenon-magnetic material that is left after pole trimming is between about0.3 and 0.9 microns.

2^(nd) Embodiment (Planar Writer)

Referring now to FIG. 7, the process begins with the provision of lowermagnetic pole 71 (for purposes of simplification, elements 13, 24, 25,and 26 are shown as single element 71) in which we form a cavity(extending downwards from the top surface for between about 2.5 and 35microns) which contains write coils 14. The latter are coated with layerof insulation 17 b so that the cavity that contains the coils is justfilled. Also shown in FIG. 7 is a step just to the left of cavity edge81. The distance between the top and bottom surfaces of this step istypically between about 1.5 and 2.5 microns.

A photoresist mold (not shown) is then formed which covers all surfacesexcept an area that extends from edge 81 of the cavity to a distancethat is sufficient to leave fully exposed the step described immediatelyabove (which can be seen to be covered by element 28 in FIG. 2).

Then, through electroplating, layer of non-magnetic material 88 isdeposited to a thickness sufficient to cover all of the above-describedstep (just behind where the ABS, marked by broken line 82, willeventually be), generally to a thickness between about 1.5 and 2.5microns. Our preferred materials for electroplated layer 88 have beenany of NiPd, NiP, or NiCu, but any non-magnetic electro-platablematerial could have been used. The mold used to contain the electroplateis then removed and the surface is planarized (using CMP) until layers88, 71, and 17 b all have coplanar top surfaces.

Finally, as seen in FIG. 9, upper magnetic pole 91 is formed on theplanarized surface and the upper and lower magnetic poles, 91 and 71, aswell as layer of non-magnetic material 88, are simultaneously polishedthe plane marked by arrow 82 is reached so that a small thickness oflayer 88 remains, thereby forming the air bearing surface withoutstressing either of the magnetic poles.

The final structure is as seen in FIG. 2 except that element 28 is now(non-magnetic) metal rather than alumina. Because it was depositedthrough electroplating, the replacement for element 28 has good stepcoverage and polishing may be terminated arbitrarily close to pole 26without stressing it. Typically the thickness (in a direction normal tothe ABS) of the non-magnetic material that is left after pole trimmingis between about 0.3 and 0.5 microns.

1. A method to protect a magnetic write head during pole trimming,comprising: providing upper and lower magnetic poles that surround awrite coil, one of said poles being recessed relative to the otherwhereby there is a step between them; electroplating a layer ofnon-magnetic material to fully cover said step; and then simultaneouslypolishing both poles as well as said layer of non-magnetic materialuntil an amount of said layer of non-magnetic material remains, therebyforming an air bearing surface without stressing either of said magneticpoles.
 2. The method described in claim 1 wherein said electroplatedlayer of non-magnetic material is selected from the group consisting ofNiPd, NiP, and NiCu.
 3. The method described in claim 1 wherein saidremaining amount of electroplated non-magnetic material has a thickness,in a direction normal to said air bearing surface, of between about 0.3and 0.5 microns.
 4. The method described in claim 1 wherein said layerof electroplated non-magnetic material is deposited to a thicknessbetween about 1.5 and 2.5 microns.
 5. A process to form an air bearingsurface for a LDCR magnetic write head, comprising: providing a lowermagnetic pole, having a top surface, and forming therein a cavitycontaining a write coil that projects above said cavity; coating saidcoil with a layer of insulation and a seed layer and thereby fillingsaid cavity; coating said seed layer and said lower pole top surfacewith a layer of a positive photoresist; by exposing through a first maskand then performing a first development, forming from said layer ofphotoresist a first mold that surrounds the coil while leaving part ofsaid top surface exposed; through electroplating, depositing an uppermagnetic pole on said seed layer and on the exposed top surface; byexposing through a second mask and then performing a second development,forming a second mold from said first mold, thereby exposing anadditional amount of said top surface; through electroplating,depositing a layer of non-magnetic material on said upper magnetic poleand on said additional exposed top surface; then removing the secondmold; and then simultaneously polishing said lower magnetic pole andsaid layer of non-magnetic material until a thickness of said layer ofnon-magnetic material remains, thereby forming said air bearing surfacewithout stressing either of said magnetic poles.
 6. The process recitedin claim 5 wherein said write coil projects above said cavity by betweenabout 3 and 5 microns.
 7. The process recited in claim 5 wherein thepart of said top surface that is exposed inside said first mold isbetween about 2 and 4 microns.
 8. The process recited in claim 5 whereinthe part of said additional amount of the top surface that is exposedinside said second mold is between about 1 and 2 microns
 9. The processrecited in claim 5 wherein said electroplated layer of non-magneticmaterial is selected from the group consisting of NiPd, NiP, and NiCu.10. The process recited in claim 5 wherein said remaining thickness ofelectroplated non-magnetic material, in a direction normal to said airbearing surface, is between about 0.3 and 0.9 microns.
 11. The processrecited in claim 5 wherein said layer of electroplated non-magneticmaterial is deposited to a thickness between about 2 and 3 microns. 12.A process to form an air bearing surface for a planar magnetic writehead, comprising: providing a lower magnetic pole, having a first topsurface and a second top surface that is parallel to, and lower than,said first top surface, thereby forming a step; forming a cavity thatextends downwards from said first top surface and that is filled with awrite coil which is covered by a layer of insulation whose top surfaceis coplanar with said first top surface; coating said layer ofinsulation and said first and second top surfaces with a layer ofphotoresist; forming a mold from said layer of photoresist, said moldcovering all surfaces except an area that extends from an edge of saidcavity to a distance that is sufficient to fully expose said step;through electroplating, depositing a layer of non-magnetic material to athickness sufficient to cover all of said step; removing said mold andthen planarizing until said layer of non-magnetic material has a thirdtop surface that is coplanar with said first top surface; then formingan upper magnetic pole on said first and third top surfaces and on saidlayer of insulation; and then simultaneously polishing said upper andlower magnetic poles as well as said layer of non-magnetic materialuntil a thickness of said layer of non-magnetic material remains,thereby forming said air bearing surface without stressing either ofsaid magnetic poles.
 13. The process recited in claim 12 wherein saidcavity extends downwards from said first top surface for between about2.5 and 3.5 microns.
 14. The process recited in claim 12 wherein saidsecond top surface is lower than said first first top surface by betweenabout 1.5 and 2.5 microns.
 15. The process recited in claim 12 whereinsaid electroplated layer of non-magnetic material is selected from thegroup consisting of NiPd, NiP, and NiCu.
 16. The process recited inclaim 12 wherein said remaining thickness of electroplated non-magneticmaterial, measures between about 0.3 and 0.5 microns in a directionnormal to said air bearing surface.
 17. The process recited in claim 12wherein said layer of electroplated non-magnetic material is depositedto a thickness between about 1.5 and 2.5 microns.
 18. A LDCR magneticwrite head, having an air bearing surface, comprising: a lower magneticpole, having a top surface, from which there extends a cavity containinga write coil, said write coil projecting above said cavity; a layer ofinsulation coating said coil whereby said cavity is filled; anelectroplated upper magnetic pole over said layer of insulation; a layerof an electroplated non-magnetic material on said upper magnetic pole;said lower magnetic pole extending all the way to the air bearingsurface; said upper magnetic pole extending to within a distance fromsaid air bearing surface whereby there is a space between the uppermagnetic pole and the air bearing surface; and said space being filledwith said electroplated non-magnetic material.
 19. The magnetic writehead described in claim 18 wherein said write coil projects above saidcavity by between about 3 and 5 microns.
 20. The magnetic write headdescribed in claim 18 wherein said electroplated upper magnetic pole hasa thickness between about 2 and 3 microns.
 21. The magnetic write headdescribed in claim 18 wherein said electroplated layer of non-magneticmaterial is selected from the group consisting of NiPd, NiP, and NiCu.22. The magnetic write head described in claim 18 wherein said spacethat is filled with electroplated non-magnetic material has a thicknessof between about 0.3 and 0.9 microns in a direction normal to said airbearing surface.
 23. The magnetic write head described in claim 18wherein said layer of electroplated non-magnetic material on said uppermagnetic pole has a thickness of between about 2 and 3 microns.
 24. Aplanar magnetic write head having an air bearing surface, comprising: alower magnetic pole, having a first top surface and a second top surfacethat is parallel to, and lower than, said first top surface, whereby thelower write pole has upper and lower edges; a cavity that extendsdownwards from said first top surface and that is filled with a writecoil, said write coil being covered by a layer of insulation whose topsurface is coplanar with said first top surface; an upper magnetic writepole over said cavity and on said lower write pole; said upper magneticpole extending as far as said air bearing surface; said lower edge ofthe lower magnetic pole extending as far as said air bearing surface;and an electroplated layer of non-magnetic material between said upperlower pole edge and the air bearing surface.
 25. The magnetic write headdescribed in claim 24 wherein said cavity extends downwards from saidfirst top surface for between about 2.5 and 3.5 microns.
 26. Themagnetic write head described in claim 24 wherein said second topsurface is lower than said first first top surface by between about 1.5and 2.5 microns.
 27. The magnetic write head described in claim 24wherein said electroplated layer of non-magnetic material is selectedfrom the group consisting of NiPd, NiP, and NiCu.
 28. The magnetic writehead described in claim 24 wherein said electroplated layer ofnon-magnetic material between said upper pole edge and the air bearingsurface measures between about 0.3 and 0.5 microns in a direction normalto said air bearing surface.
 29. The magnetic write head described inclaim 24 wherein said electroplated layer of non-magnetic materialbetween said upper pole edge and the air bearing surface measuresbetween about 0.3 and 0.5 microns in a direction normal to said firsttop surface.